environmental behaviour of tritium released by nuclear ... · environmental behaviour of tritium...
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Environmental behaviour of
tritium released by nuclear
facilities in marine and terrestrial
ecosystems:
State-of-the-art and examples
Denis Maro (IRSN, Laboratoire de Radioécologie de
Cherbourg-Octeville
Mail: [email protected])
Task force tritium
METI, Tokyo
March 13, 2014
AREVA NC La Hague NRP
Pôle RadioProtection - ENVironnement
SErvice de recherche et d’expertise sur les RISques environnementaux
2
▌ Context
▌ Objectives
▌ Transfer of tritium in marine and terrestrial ecosystems
Importance of the knowledge of speciation (HT, HTO, OBT)
Marine ecosystem
Terrestrial ecosystem
Interface between marine and terrestrial ecosystems
▌ Conclusions
Outlines
3
▌ Context
▌ Objectives
▌ Transfer of tritium in marine and terrestrial ecosystems
Importance of the knowledge of speciation (HT, HTO, OBT)
Marine ecosystem
Terrestrial ecosystem
Interface between marine and terrestrial ecosystems
▌ Conclusions
Outlines
4
▌ Except for rare gases, the amounts (Bq) of tritium from
controlled release are higher than for other radionuclides (10-100
times)
▌ Increase of tritium releases in France
Tritium is released by Nuclear Power Plants (NPP), Nuclear Reprocessing Plants
(NRP, e.g. AREVA NC La Hague), research centers and defense facilities;
In the future, the releases will increase with the commissioning of new built
nuclear facilities like the Laser Megajoule (LMJ), the European Pressurized
Reactor (EPR) and the International Thermonuclear Experimental Reactor
(ITER).
▌ Uncertainties on transfers in marine and terrestrial ecosystems
existing uncertainties on transfer knowledge in marine and terrestrial
ecosystems, e.g. transfer kinetics of tritiated water (HTO), tritiated hydrogen
(HT) and Organically Bound Tritium (OBT) in the different compartments of
ecosystems.
▌ Anticipate concerns from the public
Context
▌Why is it important to study the transfer of tritium in the
environment?
5
Context
5
▌ Main document in France, white paper on tritium (2010),
coordinated by ASN (French Nuclear Safety Authority): see lecture
on tritium “the French situation” by J. L. Lachaume (ASN, Deputy
Director General) at METI.
http://www.asn.fr/sites/tritium/plus/english-version.html
Written by a group of
experts with various
backgrounds
(governmental experts,
operators, experts from
non-governmental
laboratories): The
white paper
encompasses the state
of the art and
recommendations from
IRSN dedicated to the
environmental impact
of tritium
6
▌ Context
▌ Objectives
▌ Transfer of tritium in marine and terrestrial ecosystems
Importance of the knowledge of speciation (HT, HTO, OBT)
Marine ecosystem
Terrestrial ecosystem
Interface between marine and terrestrial ecosystems
▌ Conclusions
Outlines
7
▌ Increase knowledge on the quantification (e.g. fluxes) of
tritium transfers in marine and terrestrial ecosystems with a
focus on speciation and kinetic of OBT build up:
Estimation of tritium turnover in aquatic biota: e.g. marine
seaweed, marine invertebrates such as shellfish, fish ;
Quantification of tritium in grassland ecosystem: kinetic of OBT
biosynthesis throughout the human food chain; dry and wet
deposition;
▌ Improve tritium transfer models between the source of release
and the different components of the ecosystems (seawater:
MARS, atmosphere: TOCATTA);
Objectives
… to have a more realistic human dose assessment.
8
▌ Context
▌ Objectives
▌ Transfer of tritium in marine and terrestrial ecosystems
Importance of the knowledge of speciation (HT, HTO, OBT)
Marine ecosystem
Terrestrial ecosystem
Interface between marine and terrestrial ecosystems
▌ Conclusions
Outlines
9
▌ Tritium speciation of atmospheric or aquatic releases and
bioavailability:
HTO (tritiated water): bioavailable for species with high exchange velocity (few
hours) with TFWT;
Organic molecules: bioavailability depends on the molecule;
HT (tritiated hydrogen in the atmospheric releases): not bioavailable for species
but can be oxidized by biogeochemical reactions and become bioavailable.
Importance of the knowledge of the speciation
▌ Tritium is present into biota mainly in two forms:
TFWT (Tissue Free Water Tritium): tritium is incorporated with water exchanges;
Quick exchange with the environment (~hour);
OBT (Organically Bound Tritium): tritium is incorporated with biochemical
processes;
Relatively slow exchange with the environment (~month).
10
Importance of knowledge of the speciation
▌ Example of speciation in AREVA NC La Hague NRP atmospheric
plume in the environment: how can we study the speciation?
Sampling
Sampling particles on
filter
(PIAF)
Sampling water vapor
(H3R7000)
Air sampling
(pressurized bottle)
Treatment
Dilution in cocktail
Mixing with cocktail
HT and total tritium
extraction and mixing
with cocktail
Measurement
Liquid scintillation
Physico-chemical forms
Taero
HTO
HT
Torg
H3R7000
(IRSN, Navy patent)
PIAF
Bottle
B20
In Lab
extraction
11
Importance of the knowledge of the speciation
▌ Example of speciation in AREVA NC La Hague NRP atmospheric
plume (in 2013 ~ 6.0 1013 Bq year-1)
83 % of T released by the NRP is in the form of HT
12
▌ Context
▌ Objectives
▌ Transfer of tritium in marine and terrestrial ecosystems
Importance of the knowledge of speciation (HT, HTO, OBT)
Marine ecosystem
Terrestrial ecosystem
Interface between marine and terrestrial ecosystem
▌ Conclusions
Outlines
13
▌ Behaviour of tritium in the marine environment
Marine ecosystem: schematic transfer pathways
Evaporation, diffusion, sea pray Dry deposition Rain
Wet deposition
Marine release
(HTO)
Advection
Diffusion
Wind friction
TFWT/OBT
Biochemical processes:
photosynthesis, tritium/hydrogen
exchange
Biochemical processes:
food web,
tritium/hydrogen
exchange
TFWT/OBT
TFWT/OBT
14
▌ Liquid releases in the English Channel by AREVA NC: HTO
Marine ecosystem: liquid releases from La Hague NRP
Annual releases are quite stable ~ 1.2 1016 Bq year-1
-12 -10 -8 -6 -4 -2 0 2 4 6 8 1046
48
50
52
54
56
58
60
GrandeBretagne Hollande
Norvège
Ecosse
Skagerrak
Danemark
Irlande
Allemagne
Merdu Nord
Manche
Merd'Irlande
MerCeltique
ChenalSt George
Shetland
Belgique
France
°Lat.
Flamanville
Paluel Penly
Gravelines
La Hague
Cardiff
Sellafield
°Long.
Winfrith Dungeness
Les casquets
One PWR NPP: 1/100 of La Hague
NRP release
15
Marine ecosystem: radionuclides dispersion
Septembre 1994
Gedymac campaignSeptember 1994
150
250
350
450
550
650
750
850
950
1050
1150
1300
1750
2500
3500
4500
5500
6500
7500
Bq / m3
SIMULATION
MEASUREMENTS
Tritium(no input from the Seine river)
▌ Model validation of hydrodynamic dispersion
(numerous in-situ measurements vs. modeling)
Average dilution coefficient close to the outfall of La Hague (Goury) - NRP is well known
~ 0,76 Bq m-3 per TBq year-1
R/V Côtes de la Manche
Automatic sampler
La Hague NRP
Goury
16
▌ Concentration in water: hydrodynamic modeling
Marine ecosystem: hydrodynamic modeling and validation
Real discharges and meteorology,
one frame every 15 min
MARS model frames and mesh sizes
-20 -15 -10 -5 0 5 10
40
45
50
55
60
65
Rank 05600 m
Rank 11500 m
Rank 2350 m
Rank 3110 m
0 m
500 m
1000 m
1500 m
2000 m
2500 m
3000 m
3500 m
4000 m
4500 m
5000 m
5500 m
0 m
10 m
20 m
30 m
40 m
50 m
60 m
70 m
80 m
90 m
100 m
110 m
120 m
130 m
140 m
150 m
Bathymetry
After model validation, the uncertainties for individual measurements are around 50%
(the model is highly reliable)
17
▌ Concentration in marine biota near the point of release
Marine ecosystem: transfer to biota
Around 10 Bq L-1 (TFWT, OBT) for 1.2 1016 Bq year-1
Mean 11.1 11.2 10.7 1.0
18
▌ Concentration in seaweed as function of water concentration
Marine ecosystem: transfer in biota and his modeling
Steady state between seawater and seaweed TFWT is rapidly achieved while transfer
between HTO and OBT is much slower: need to take this into account when modeling
0
5
10
15
20
25
30
35
May-0
9
No
v-09
May-1
0
No
v-10
May-1
1
No
v-11
Bq.L-1
Date
HTO in Fucus serratus
Seawater HTO
Seaweed HTO
0
5
10
15
20
25
30
35
May-0
9
No
v-09
May-1
0
No
v-10
May-1
1
No
v-11
Bq.L-1
Date
OBT in Fucus serratus
Seawater HTO
Seaweed OBT
transfer model
Transfer parameters OBT/HTO(steady state), expecting 1 t1/2bio (day)
half-life
Fucus serratus 0.78 [0.76-0.82] 128 [99-175]
Fiévet B., Pommier J., Voiseux C., Bailly du Bois P., Laguionie P., Cossonnet C., Solier L. (2013) Transfer of tritium released into the marine
environment by French nuclear facilities bordering the English Channel. Environmental Science & Technology 47(12): 6693-6703.
19
Marine ecosystem: dispersion around Fukushima NPP
▌ Estimation of 137Cs quantities from measurements
137Cs quantities were estimated on the basis of individual measurements in a 50 x 100
km (100-1000 measurements for each period) area around the plant (issues: depth,
mixing layer, atmospheric fallout, rain water washout, …)
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
02468101215192329364556698610013016020025031039048060074092011001400170021002700
Bq.L-1
April 11 - 18
Fukushima Dai-ichi
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
April 18 - 25140.8 141 141.2 141.4 141.6
April 25 - May 02
Fukushima Dai-ichi
140.8 141 141.2 141.4 141.6
May 02 - 16
Fukushima Dai-ichi
a b c d
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
02468101215192329364556698610013016020025031039048060074092011001400170021002700
Bq.L-1
Fukushima Dai-ichi
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
Blue frame: area for integration of 137Cs quantities : Sampling locations
e f g hMay 16 - 30 May 30 - June 13 June 13 - 27 June 27 - July 11
0 km 20 km 40 km 60 km
Interpolated
137Cs
concentrations
from April 11
to July 11
20
Marine ecosystem: dispersion around Fukushima NPP
▌ Estimation of the rate of seawater renewal
Environmental half-time exponential decay t1/2 = 6.9 days
This source-term could be used in numerical dispersion models
Constant dilution by clean water
through marine currents due to
convergence of Kuroshio and
Oyashio currents:
Seasonal changes in the
ocean circulation ?
Return of contaminated
water back in the area ?
Exponential decay back
extrapolated to April 8:
22 PBq
Main incertitude: depth of the
mixing layer
Evolution of 137Cs quantities measured in
seawater
21
Marine ecosystem: dispersion around Fukushima NPP
▌ Flux estimation of 137Cs from direct releases and the dilution
coefficient
Fluxes of 137Cs could be deduced from concentrations by applying the factor: 1.06 1011
Bq released per Bq L-1 measured
Conversely, concentrations could be estimated from fluxes
1E1
1E2
1E3
1E4
1E5
Caes
ium
137
, Bq/
L
1E12
1E13
1E14
1E15
1E16
Caes
ium
137
, Bq/
day
20/03 27/03 03/04 10/04 17/04 24/04 01/05 08/05 15/05 22/05 29/05 05/06 12/06 19/06 26/06 03/07 10/07 17/07
30 m North of Fukushima Dai-ichi
Evolution of concentrations and
corresponding fluxes of 137Cs in seawater
Assumptions:
• Measurements close to the
plant are representative of
the released flux;
• Amount of 22 PBq
corresponds to the
quantity of 137Cs released
from March 26 to April 8;
(average concentration:15
716 Bq.L-1, number of
values = 28, duration =
13.2 days);
• Right Y axis in figure shows
this conversion.
Total direct release until
July 18 -> 27 PBq
(12 PBq -> 41 PBq)
Bailly du Bois P., Laguionie P., Boust D., Korsakissok I., Didier D., Fiévet B. 2011. Estimation of marine source-term following Fukushima Dai-ichi
accident. Journal of environmental Radioactivity. DOI:10.1016/j.jenvrad.2011.11.015
22
▌ Context
▌ Objectives
▌ Transfer of tritium in marine and terrestrial ecosystems
Importance of the knowledge of speciation (HT, HTO, OBT)
Marine ecosystem
Terrestrial ecosystem
Interface between marine and terrestrial ecosystems
▌ Conclusions
Outlines
23
▌ Behaviour of tritium in the terrestrial environment
Terrestrial ecosystem: schematic transfer pathways
Background level in North hemisphere < 1 Bq L-1 water vapor (10-2 Bq m-3 air)
HT/HTO
Turbulent diffusion
Transport
HT
HT
Soil diffusion
HTO
Bacterial oxidation
Photolysis
HTO
TFWT OBT
Photosynthesis
Root uptake
Release
HT/HTO
Evaporation
Dry deposition
HTO
Stomatal exchange
Transport/Diffusion to the groundwater
Wet deposition
Rain
HTO
HTO
24
▌ Gaseous release in the atmosphere by AREVA NC: HTO/HT
Terrestrial ecosystem: gaseous releases from La Hague NRP
Gaseous release decrease: in 2013 ~ 6.0 1013 Bq year-1
AREVA NC NRP LA
HAGUE
Wind conditions 2008 - "Omonville La Petite".
Wind speed (m.s-1) and Direction (°)
0
2
4
6
8
10
360
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
fréq dir (%)
One PWR NPP: 1/50 of La Hague
NRP release
In field experiment
25
Terrestrial ecosystem: radionuclides dispersion
▌ Model validation: krypton 85 as a tool to validate atmospheric
dispersion modeling
Atmospheric Transfer Coefficient (ACT) ~ 3 10-6 s m-3
Automatic sampler
Captive balloon
Strong discrepancy between models
and measurements
Leroy C., Maro D., Hébert D., Solier L., Rozet M., Le Cavelier S. and Connan O. (2010). A study of the atmospheric dispersion of a high release of
krypton-85 above a complex coastal terrain, comparison with the predictions of Gaussian models (Briggs, Doury, ADMS4). Journal of Environmental
Radioactivity, 101, 11, 937-944.
26
▌ Concentration in the atmosphere: Gaussian modeling
Terrestrial ecosystem: dispersion modeling and validation
After model validation the uncertainties are below a factor of 3 for in all meteorological
conditions
Source
(stack)
Standard
deviation
of plume
Wind direction
Y
X
Z
Plume axis
Gaussian modeling
27
▌ “In field experiment” technical platform (2 km downwind
distance) to study tritium transfer (kinetics of OBT, dry and
wet deposition, microbial oxidation of HT in soil)
Terrestrial ecosystem: transfer to biota
27/19
Continuously Recording Field Monitor for 85Kr
10 m mast with sonic anemometer (turbulence & wind)
Weather station
Lab
CO2/H2O measurement acquisitions
(LICOR 7000)
Grass and soil (unsaturated
zone)
14C/3H trapping device (bubbling)
Lysimeters
28
▌ Concentration in grass around the NRP: “In field experiment”
technical platform (2 km downwind distance)
Terrestrial ecosystem: concentration to biota
around 10 Bq L-1 for 6.0 1013 Bq year-1
▌ In La Hague area, concentrations in vegetable are in the
same order of magnitude
29
▌ Modeling of tritium transfer in terrestrial ecosystem
(TOCATTA), a part of the SYMBIOSE Platform
Terrestrial ecosystem: transfer to biota and modeling
SOURCE Gas dispersion
(HTO)
Wet input (HTO,
via precipitation)
Interception by
soil
Wet input (HTO,
via precipitation)
Interception by
plant
CANOPY
ATMOSPHERE
Soil surface
exchange (HTO)
Foliar diffusion
(TFWT)
Photosyn
-thesis
SOIL WATER (HTO)
Radioactive decay
Root uptake
(HTO)
PLANT WATER
(TFWT)
Radioactive
decay
Net formation
(OBT)
PLANT DRY
MATTER (OBT)
Radioactive
decay
Shoot
structural
dry matter
Ageing Cutting
(grass)
Root
structural
dry matter
Ageing
Biological
growth
Biological
growth
Substrate
(sap)
Respiration
REST OF
PLANT
SINK
TOCATTA is a hourly time-step model, implemented within the SYMBIOSE
modeling platform
Le Dizès S., Aulagnier C., Henner P., Simon-Cornu M. (2013) TOCATTA: a dynamic transfer model of 3H from the atmosphere to soil–plant systems.
Journal of Environmental Radioactivity, 124: 191-204.
30
▌ Context
▌ Objectives
▌ Transfer of tritium in marine and terrestrial ecosystems
Importance of the knowledge of speciation (HT, HTO, OBT)
Marine ecosystem
Terrestrial ecosystem
Interface between marine and terrestrial ecosystems
▌ Conclusions
Outlines
31
Interface between marine/terrestrial ecosystems
▌ Tritium evaporation and partial pressure equilibrium induce
transfer between water and the atmosphere
Near the shore the atmospheric tritium concentration due to seawater is around 5
Bq L-1 of water vapor
Atmospheric release
Liquid release
Main wind
direction
Transect
Maro D., Tenailleau L., Fontugne M., Germain P., Hébert D. and Rozet M. (2005). Tritium transfer between sea and atmosphere in the English
Channel (North Contentin and Bay of Seine). Radioprotection, 40, 1, 589-594.
32
▌ Context
▌ Objectives
▌ Transfer of tritium in marine and terrestrial ecosystems
Importance of the knowledge of speciation (HT, HTO, OBT)
Marine ecosystem
Terrestrial ecosystem
Interface between marine and terrestrial ecosystems
▌ Conclusions
Outlines
33
▌ What do we need to estimate the human dosimetric impact of
tritium releases into the environment?
Speciation of releases (HTO/HT/organic molecule): Tritium
released in the environment as HTO behaves like H from H20.
The transfer to the biota, is very quick (hours) for TFWT and
slower (months) for OBT;
Dispersion: validation of dilution coefficients or dilution
models are prerequisites to estimate the transfer to biota
(e.g. Fukushima, 1.06 1011 Bq released per Bq L-1 measured);
Transfer to biota: a constant ratio 3H/H is kept in all
compartments of the environment (e.g. water/air and
TFWT/OBT);
Water to atmosphere: this pathway could be taken into
account for population close to seawater.
Conclusions: evaluation
34
▌ Monitoring the tritium concentrations in the environment:
Water: direct sampling;
Air: HTO by cold trap (e.g. H3R7000) and speciation by
bubbling device (e.g. MARC 7000);
Biota and specifically food web: freeze drying to separate
TFWT and OBT (combustion water extraction from dry
matter).
▌ Measurement by counting scintillation (DL ~ 1 Bq L-1). For
lower levels: 3He ingrown (Mass Spec);
▌ For example, in the vicinity of La Hague NRP, average tritium
concentrations are 10 Bq L-1 in the marine and the terrestrial
ecosystems.
Conclusions: monitoring
Maro D. and Baron Y. (2007). Patent WO2008003853 A2. Method for automatically sampling tritium in the water vapour in air (PREVAIR).
Maro D and Hébert D. (2013). Patent FR 135319. System for the speciation of chemical forms of tritium from air (TRITAIR).
35
▌ This methodology was used by North-Cotentin Radioecology
Group:
Indeed, epidemiological studies have shown in 1997 a trend
towards an excess number of leukaemia cases in the region of
Nord-Cotentin (France) and it was suggested that the risk of
leukaemia was associated with some aspects of lifestyle;
To respond to public concern, the French Ministries of the
Environment and Health decided to commission
complementary epidemiological studies and a detailed
radioecological analysis;
The radioecological study was entrusted to a group of experts
with various backgrounds (inspectors, governmental experts,
operators, experts from non-governmental laboratories and
foreign experts)-the North-Cotentin Radioecology Group;
Its principal objective was to estimate the exposure levels to
ionizing radiation and associated risk of leukemia for
populations in the Nord-Cotentin.
Conclusions: an example of stakeholders involvement in France
36
Conclusions: application
Farmer (Digulleville)
3H
14C
129I
99Tc
106RuRh
Fisherman (Goury)
3H
14C
129I
99Tc
106RuRh
▌ Example, the gaseous/liquid releases contribution to the dose to the
public in 2010: 8.7 µSv y-1 for the farmer and 4.7 µSv y-1 for the
fisherman
Gaseous releases: 3H contribution ~ 1% for 57 TBq y-1
Liquid releases: 3H contribution ~ 1% for 10 000 TBq y-1
3H dose: 6.3 10-2 µSv y-1 3H dose: 2.4 10-2 µSv y-1
3H dose: 2.6 10-3 µSv y-1 3H dose: 9.6 10-3 µSv y-1
Farmer (Digulleville)
3H
14C
129I
85Kr
37
▌ In France tritium releases will increase in the future with new
built nuclear facilities.
▌ ASN has coordinated a work on tritium (White book, 2010) and
recommended to improve knowledge on tritium transfers in the
ecosystems: see lecture on tritium “the French situation” by J.
L. Lachaume (ASN, Deputy Director General) at METI.
▌ IRSN studies tritium behaviour to have more realistic dose
assessment for human and biota.
▌ Uncertainties remain in the marine and terrestrial ecosystems
(kinetic of OBT formation, wet deposition…).
▌ IRSN will carry on developing specific programs on these topics
(e.g. VATO project).
Conclusions: general
38
▌ How can IRSN help for calculating dosimetric impact of
controlled release of tritium?
IRSN has developed up-to-date parameterized models of tritium
transfers in marine & terrestrial ecosystems where various
scenarios can be tested and compared in terms of resulting
human dosimetric impact, including sensitivity and uncertainty
analyses;
IRSN has developed sampling methodologies for environmental
monitoring of tritium in various compartments and ecosystems;
IRSN has developed low-level tritium metrology adapted to
environmental monitoring.
Conclusions: IRSN